Hình nền hạt phân tử chuyển động tương tác với trỏ chuột bằng Javascript

Tết Pro tháng 6 23, 2019 4 min read

Tạo hình nền tối với CSS

<style>
  body { background-color:#222;}
</style>

Tạo các hạt phân tử bằng Javascript

<script type="text/javascript" color="255,255,255" opacity='0.7' zIndex="-2" count="300" src="canvas-nest.js"></script>

! function() {
 //封装方法，压缩之后减少文件大小
 function get_attribute(node, attr, default_value) {
  return node.getAttribute(attr) || default_value
 }
 //封装方法，压缩之后减少文件大小
 function get_by_tagname(name) {
  return document.getElementsByTagName(name)
 }
 //获取配置参数
 function get_config_option() {
  var scripts = get_by_tagname("script"),
   script_len = scripts.length,
   script = scripts[script_len - 1]; //当前加载的script
  return {
   l: script_len, //长度，用于生成id用
   z: get_attribute(script, "zIndex", -1), //z-index
   o: get_attribute(script, "opacity", .5), //opacity
   c: get_attribute(script, "color", "0,0,0"), //color
   n: get_attribute(script, "count", 99) //count
  }
 }
 //设置canvas的高宽
 function set_canvas_size() {
  canvas_width = the_canvas.width = window.innerWidth || document.documentElement.clientWidth || document.body.clientWidth, 
  canvas_height = the_canvas.height = window.innerHeight || document.documentElement.clientHeight || document.body.clientHeight
 }

 //绘制过程
 function draw_canvas() {
  context.clearRect(0, 0, canvas_width, canvas_height);
  //随机的线条和当前位置联合数组
  var all_array = [current_point].concat(random_lines);
  var e, i, d, x_dist, y_dist, dist; //临时节点
  //遍历处理每一个点
  random_lines.forEach(function(r) {
   r.x += r.xa, 
   r.y += r.ya, //移动
   r.xa *= r.x > canvas_width || r.x < 0 ? -1 : 1, 
   r.ya *= r.y > canvas_height || r.y < 0 ? -1 : 1, //碰到边界，反向反弹
   context.fillRect(r.x - 0.5, r.y - 0.5, 1, 1); //绘制一个宽高为1的点
   for (i = 0; i < all_array.length; i++) {
    e = all_array[i];
    //不是当前点
    if (r !== e && null !== e.x && null !== e.y) {
      x_dist = r.x - e.x, //x轴距离 l
      y_dist = r.y - e.y, //y轴距离 n
      dist = x_dist * x_dist + y_dist * y_dist; //总距离, m
     dist < e.max && (e === current_point && dist >= e.max / 2 && (r.x -= 0.03 * x_dist, r.y -= 0.03 * y_dist), //靠近的时候加速
      d = (e.max - dist) / e.max, 
      context.beginPath(), 
      context.lineWidth = d / 2, 
      context.strokeStyle = "rgba(" + config.c + "," + (d + 0.2) + ")", 
      context.moveTo(r.x, r.y), 
      context.lineTo(e.x, e.y), 
      context.stroke())
    }
   }
   all_array.splice(all_array.indexOf(r), 1)

  }), frame_func(draw_canvas)
 }
 //创建画布，并添加到body中
 var the_canvas = document.createElement("canvas"), //画布
  config = get_config_option(), //配置
  canvas_id = "c_n" + config.l, //canvas id
  context = the_canvas.getContext("2d"), canvas_width, canvas_height, 
  frame_func = window.requestAnimationFrame || window.webkitRequestAnimationFrame || window.mozRequestAnimationFrame || window.oRequestAnimationFrame || window.msRequestAnimationFrame || function(func) {
   window.setTimeout(func, 1000 / 45)
  }, random = Math.random, 
  current_point = {
   x: null, //当前鼠标x
   y: null, //当前鼠标y
   max: 20000
  };
 the_canvas.id = canvas_id;
 the_canvas.style.cssText = "position:fixed;top:0;left:0;z-index:" + config.z + ";opacity:" + config.o;
 get_by_tagname("body")[0].appendChild(the_canvas);
 //初始化画布大小

 set_canvas_size(), window.onresize = set_canvas_size;
 //当时鼠标位置存储，离开的时候，释放当前位置信息
 window.onmousemove = function(e) {
  e = e || window.event, current_point.x = e.clientX, current_point.y = e.clientY
 }, window.onmouseout = function() {
  current_point.x = null, current_point.y = null
 }
 //随机生成config.n条线位置信息
 for (var random_lines = [], i = 0; config.n > i; i++) {
  var x = random() * canvas_width, //随机位置
   y = random() * canvas_height,
   xa = 2 * random() - 1, //随机运动方向
   ya = 2 * random() - 1;
  random_lines.push({
   x: x,
   y: y,
   xa: xa,
   ya: ya,
   max: 6000 //沾附距离
  })
 }
 //0.1秒后绘制
 setTimeout(function() {
  draw_canvas()
 }, 100)
}();